Which numerical setup can be used to calculate the atomic mass of gallium

Gallium (Ga) is an element in the periodic table with the atomic number, 31.

Atomic number is the number of protons in an atom while atomic mass is the total number of protons and neutrons present in the nucleus of an atom. The mass of an electron is not considered while determining the mass of an atom because its mass is negligible. Hence, the numerical set up that can be used to calculate the atomic mass of gallium (Ga) is

atomic number of Ga (31) + the number of neutrons present in the nucleus (38)

The addition of the above gives 69 which is the atomic mass of gallium (Ga)

69.723 u ± 0.001 u should be your answer.